Comparison of Insulin and Glucose Metabolism in Horses with Pituitary Pars Intermedia Dysfunction Treated Versus Not Treated with Pergolide

Equine pituitary pars intermedia dysfunction (PPID) is known to alter glucose/insulin metabolism. This study evaluated changes in parameters relating to glucose/insulin metabolism and determined whether there is a difference between pergolide-treated and untreated animals. We hypothesized that glucose/insulin dynamics in PPID horses receiving pergolide would be different than those in untreated horses. A total of 38 horses with diagnoses of PPID were included in the study (average age: 24 years). A total of 25 horses were untreated; 13 horses were treated with pergolide (>3 months). Parameters relating to glucose/insulin metabolism were determined in all horses, as follows: adrenocorticotropin-releasing hormone (ACTH), insulin, fructosamine, triglyceride, glucose, modified insulin-to-glucose ratio (MIRG), and reciprocal of the square root of insulin (RISQI). A combined glucose-insulin test (CGIT) was performed in 23 horses as not all owners agreed to the testing. Treated animals showed a tendency to have lower ACTH, but results were not significant. All animals had fructosamine levels exceeding reference values (mean value 314 ± 32 μmol/L; reference range: <280 μmol/L). There were no statistically significant differences between insulin, glucose, ACTH, triglycerides concentrations, RISQI/MIRG calculations, and CGIT results of pergolide-treated PPID and those of untreated horses. Five horses (13.2%) had combined hyperglycemia/hyperinsulinemia, whereas 7 horses (18.4%) displayed hyperglycemia, and 3 horses (7.9%) showed hyperinsulinemia alone. Forty percent of the horses with altered glucose/insulin metabolism were treated with pergolide. Based on RISQI and MIRG calculations, 19 animals displayed changes in glucose/insulin metabolism. Fourteen of twenty-three horses (61%) showed signs of insulin resistance in CGIT results. In conclusion, PPID horses frequently show alterations in glucose/insulin metabolism, but no significant differences were found between treated and untreated animals. Changes in insulin/glucose dynamics may not be a useful indicator of response to pergolide treatment.     

Seasonal Variation in Serum Concentrations of Selected Metabolic Hormones in Horses

Background: Determination of adrenocorticotropic hormone (ACTH) concentration is a commonly used test in the evaluation of endocrine causes of equine laminitis, but the concentration in healthy horses can be high at certain times of year, which alters the specificity of the ACTH test. Objective: To determine if circulating concentrations of ACTH, cortisol, glucose, insulin, and thyroxine vary month to month in healthy horses and in horses with equine metabolic syndrome (EMS). Animals: Nine healthy adult horses were studied on their farm/stable over the course of 1 year. After the diagnosis of EMS, 10 laminitic horses residing at the same farm/stable were also studied. Methods: Prospective study of healthy and laminitic horses. Plasma/serum samples were analyzed for concentrations of hormones and glucose. Results: ACTH was the only analyte to show a discrete seasonal pattern, with concentrations in healthy and EMS horses frequently outside of the reference range (9–35 pg/mL) in August through October. Insulin was elevated (>40 μIU/mL) in EMS horses during most months and median serum glucose was generally higher in EMS horses (100 mg/dL, range, 76–163 mg/ dL) than in controls (94 mg/dL, range, 56–110 mg/dL), but no seasonal patterns for insulin or glucose were found. Conclusions and Clinical Importance: An increased ACTH concentration in horses in late summer or autumn should be interpreted with caution. In contrast, insulin concentration is maintained within the reference range throughout the year in healthy horses, thus an increased insulin concentration at any time of year should raise suspicions of EMS, ECD, or both.     

Circadian and circannual rhythms of cortisol,ACTH, and α-melanocyte-stimulating hormone in healthy horses

Cosinor analysis was used to evaluate whether pituitary and adrenal hormones exhibit circadian rhythmicity in horses. The effect of season and animal age on their respective rhythms was also determined. In addition, the usefulness of evaluating cortisol rhythmicity for the diagnosis of pituitary pars intermedia dysfunction (PPID) was assessed. Serum cortisol concentrations (P < 0.01), but not plasma ACTH or α-melanocyte-stimulating hormone (α-MSH), showed a significant circadian periodicity in horses. An effect of season on hormone concentration was observed with plasma ACTH and α-MSH concentration greater in the fall and cortisol concentration greater in the spring (P < 0.001). Age did not affect cortisol rhythm, but it did blunt the variation in cortisol concentration in horses, similar to what has been previously reported to occur in aged people and dogs. In addition, our results suggest that clinically and diagnostically normal, non–PPID-affected horses commonly have a loss of cortisol diurnal rhythm. Therefore, measurement of circadian rhythm is not an appropriate diagnostic test for PPID.     

Pharmacokinetic and pharmacodynamic properties of pergolide mesylate following long‐term administration to horses with pituitary pars intermedia dysfunction

The objective of this study was to gain an understanding of the pharmacokinetic and pharmacodynamic properties of pergolide in horses with PPID after of long‐term oral administration. Six horses with confirmed PPID were treated with pergolide (Prascend^®) at 1 mg/horse po q24 h for 2 months, followed by 2 mg/horse po q24 h for 4 months. Following the last dose, plasma samples were collected for measurement of pergolide using an LC/MS/MS method and ACTH measurement using a chemiluminescent immunoassay. Noncompartmental and compartmental pharmacokinetic analyses were performed, as well as pharmacodynamic assessment of the effect of plasma pergolide concentrations on plasma ACTH concentrations. Pergolide effectively decreased plasma ACTH concentration in aged horses with PPID, with similar pharmacokinetic properties as reported in young horses, including an approximate terminal half‐life of 24 h. Plasma ACTH concentration increased by 50% in 3/6 horses at 2 days and 6/6 horses 10 days after discontinuing drug administration. Pergolide was quantified in all horses at 2 days and in none at 10 days after last dose. In summary, after discontinuing pergolide treatment, plasma ACTH concentration increased while pergolide was still quantifiable in some horses. Once‐daily dosing of pergolide is likely appropriate in most horses with PPID for regulating the plasma ACTH concentration.     

Comparative endocrinological responses to short transportation of Equidae (Equus asinus and Equus caballus)

In order to evaluate the effects of short transportation on β‐endorphin, adrenocorticotropic hormone (ACTH) and cortisol changes, 12 healthy stallions of Equidae (Equus asinus and Equus caballus) were studied before and after transportation of 50 km. Blood samples were collected 1 week before transportation in basal conditions, immediately before loading and after transportation and unloading, on their arrival at the breeding station. Compared to basal and before values, donkeys showed an increase in circulating ACTH (P < 0.001) and cortisol (P < 0.0005) levels after transportation and higher ACTH (P < 0.01) levels than horses after transportation. A positive and significant correlation (r = 0.885; P < 0.01) between ACTH and cortisol levels after transportation was found. No significant differences were observed for β‐endorphin levels. Compared to basal and before values, horses showed higher cortisol (P < 0.005) levels after transportation and no significant differences were observed for ACTH and β‐endorphin levels in donkeys. Horses facing forward (direction of travel) showed higher (P < 0.01) β‐endorphin levels after transportation than donkeys; horses facing backward (the opposite direction of travel) showed lower (P < 0.05) ACTH levels after transportation. The results indicate that short transportation induces a preferential activation of the hypothalamus‐pituitary‐axis (HPA), with significant release of ACTH and cortisol in donkeys and only of cortisol in horses, suggesting that transportation for donkeys may be more stressful than horses.     

Reference Values on Serum Biochemical Parameters of Brazilian Donkey (Equus asinus) Breed

Seventeen serum biochemical variables were determined in 40 donkeys of the Brazilian breed (34 females and 6 males) aged from 3 to 19 years. Mean ± standard deviation (SD) (minimum–maximum) values, obtained by automated analysis, were as follows: glucose, 58.35 ± 10.40 (44.00–90.00) mg/dL; cholesterol, 88.41 ± 9.86 (73.58–124.26) mg/dL; serum protein, 6.82 ± 0.40 (6.00–7.52) g/dL; albumin, 3.13 ± 0.21 (2.65–3.69) g/dL; creatinine, 1.80 ± 0.14 (1.51–2.19) mg/dL; urea, 24.25 ± 5.37 (14.12–34.39) mg/dL; lactate, 20.10 ± 4.58 (12.99–33.47) mg/dL; aspartate aminotransferase (AST), 295.81 ± 62.79 (173.71–466.07) IU/L; creatine kinase (CK), 158.00 ± 76.94 (51.69–440.33) IU/L; γ-glutamil-transferase (GGT), 45.82 ± 13.34 (26.17–86.38) IU/L; lactate dehydrogenase (LDH), 576.02 ± 156.32 (213.53–1162.81) IU/L; alkaline phosphatase (AP), 345.36 ± 65.90 (227.25–490.16) IU/L; calcium (Ca), 8.54 ± 0.18 (8.19–8.90) mg/dL; phosphorus (P), 2.76 ± 0.38 (1.99–3.97) mg/dL; chloride (Cl), 106.05 ± 3.20 (99.00–112.00) mEq/L; sodium (Na), 121.50 ± 4.14 (116.00–132.00) mEq/L; and potassium (K), 3.70 ± 0.42 (2.80–4.40) mEq/L. Comparisons of biochemical ranges obtained for the Brazilian donkey breed with reference ranges for other donkey breeds suggested that most values were similar. Biochemical values determined in the present study serve as reference ranges for donkey populations and can be used for health control and diagnosis of diseases.     

Comparative pharmacokinetics of meloxicam in clinically normal horses and donkeys

OBJECTIVE: To determine the disposition of a bolus of meloxicam (administered IV) in horses and donkeys (Equus asinus) and compare the relative pharmacokinetic variables between the species. ANIMALS: 5 clinically normal horses and 5 clinically normal donkeys. PROCEDURES: Blood samples were collected before and after IV administration of a bolus of meloxicam (0.6 mg/kg). Serum meloxicam concentrations were determined in triplicate via high-performance liquid chromatography. The serum concentration-time curve for each horse and donkey was analyzed separately to estimate standard noncompartmental pharmacokinetic variables. RESULTS: In horses and donkeys, mean +/- SD area under the curve was 18.8 +/- 7.31 microg/mL/h and 4.6 +/- 2.55 microg/mL/h, respectively; mean residence time (MRT) was 9.6 +/- 9.24 hours and 0.6 +/- 0.36 hours, respectively. Total body clearance (CL(T)) was 34.7 +/- 9.21 mL/kg/h in horses and 187.9 +/- 147.26 mL/kg/h in donkeys. Volume of distribution at steady state (VD(SS)) was 270 +/- 160.5 mL/kg in horses and 93.2 +/- 33.74 mL/kg in donkeys. All values, except VD(SS), were significantly different between donkeys and horses. CONCLUSIONS AND CLINICAL RELEVANCE: The small VD(SS) of meloxicam in horses and donkeys (attributed to high protein binding) was similar to values determined for other nonsteroidal anti-inflammatory drugs. Compared with other species, horses had a much shorter MRT and greater CL(T) for meloxicam, indicating a rapid elimination of the drug from plasma; the even shorter MRT and greater CL(T) of meloxicam in donkeys, compared with horses, may make the use of the drug in this species impractical.     

Pharmacology and therapeutics in donkeys

Therapeutics are often administered to donkeys based on dosage and intervals recommended for horses because very few drugs have donkey‐specific label indications. Yet differences between donkeys and horses in drug distribution, metabolism and elimination have been noted for most therapeutic agents studied. These differences can be partially explained by the donkey's unique physiology. Since their ancestors evolved in a desert environment, the modern donkey exhibits qualities that allow them to tolerate dehydration better than the horse and recover more quickly from its effects. Fluid balance and body water compartment partitioning differ from the horse and may have implications regarding drug distribution. Since donkeys are preferential browsers, differences in diet may have influenced evolutionary differences in metabolic disposition of drugs. It is important to acknowledge these differences when designing dose regimes for donkeys based on horse protocols in order to avoid either lack of efficacy or toxicity.     

Reference values on hematologic parameters of the Brazilian donkey (Equus asinus) breed

Thirteen hematologic measurements were performed on 38 healthy donkeys of the Brazilian breed (32 females and 6 males) aged 3 to 19 years. Mean ±SD (minimum-maximum) values were as follows: red blood cells (RBC) 6.82 ± 0.67 (5.46−8.17) × 10⁶/μL; packed cell volume (PCV) 37.63 ± 2.76 (32.00−44.00) %; hemoglobin (Hb) 12.87 ± 0.98 (10.70−14.50) g/dL; mean corpuscular volume (MCV) 55.45 ± 4.06 (48.90−62.70) fL; mean corpuscular hemoglobin (MCH) 18.85 ± 1.14 (17.40−21.60) pg; mean corpuscular hemoglobin concentration 34.20 ± 1.24 (31.50−36.40) g/dL; white blood cells (WBC) 8.22 ± 1.49 (4.60−11.50) × 10³/μL; bands 1.77 ± 2.00 (0.00−9.00) %; segmented neutrophils 41.18 ± 5.98 (30.50−53.20) %; lymphocytes 50.53 ± 6.25 (35.30−63.50) %; monocytes 1.57 ± 1.30 (0.00−4.60) %; eosinophils, 4.64 ± 2.17 (1.00−10.00) %; basophils 0.33 ± 0.58 (0.00−2.90) %. It was demonstrated that values of some blood parameters of the Brazilian donkey breed were similar to results obtained for other donkey breeds. The results of this study serve as reference ranges for donkey populations and can be useful for health control, which in turn helps in the diagnosis and prognosis of diseases.

Introduction

Blood examination has been performed for several reasons: as a screening procedure to assess general health; as an adjunct to patient's infection; and to evaluate the progress of certain disease states.[1] However, there are important differences in physiology, behavior, and management that influence the common diseases encountered in donkeys. Successful diagnosis and treatment often depend on recognizing these differences. [2] Unfortunately, a limited number of observations have been reported on the hematologic values for donkey breeds and populations and these studies are far from complete. [3, 4, 5, 6, 7, 8 and 9] Hematologic variation values for donkey breeds and populations should be associated with the age, sex, and the time of sampling in relation to exercise, geographic, and nutritional factors. Perhaps some of the variations observed among different authors were also associated with different techniques and methods. [4]Apart from the investigations by Perdigão de Oliveira et al,[3] Gacek et al, [10] and Mori et al, [11] we could find no published record of blood values of the Brazilian donkey breed. The aim of this investigation was to determine reference ranges for hematologic analyses in the Brazilian donkey breed to establish a baseline for further scientific and clinical use.

Materials and methods

The material for the present study consisted of 38 adult donkeys of the Brazilian breed (32 females and 6 males), ranging between 3 and 19 years of age (mean ±SD: 8.3 ± 3.5 years), from the Estação Experimental de Colina do Instituto de Zootecnia da Secretaria de Agricultura do Estado de São Paulo, and kept under similar feeding and management conditions. All animals were apparently healthy, and they were handled carefully to reduce any possible effects of stress on the parameters analyzed.Blood samples were draw from the jugular vein into 5 mL evacuated glass tubes containing EDTA as anticoagulant. Blood smears were prepared immediately after being collected from whole blood and then were air-dried. The collected blood samples were immediately stored at 4°C and processed within 6 hours.RBC and WBC counts were performed using an electronic counter (Serono Baker). Hb concentration was determined by the cyanmethemoglobin method. PCV was determined after the blood had been transferred to microhematocrit tubes and centrifuged at 10,000 g for 5 minutes. MCV, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration were calculated from PCV, Hb concentration, and RBC count.[1] Blood smears were stained with modified May-Grunwald Giemsa stain for determination of the differential WBC count. At least 200 WBCs were counted for differential WBC determinations.All analyses were performed within the Departamento de Clinica Médica da Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo.Data analysis was performed using a statistical software (Graph Pad InStat version 3.01, 32 bit for Windows 95/NT). Each parameter was tested for normality applying the Kolmogorov and Smirnov methods. The reference ranges for the hematologic analyses were given as mean ±SD and the interval from minimum and maximum values.Unpaired t-tests were used to determine the effect of sex (female versus male) on hematologic values, for data normally distributed. If data did not seem to be normally distributed, non-parametric tests (Mann-Whitney U test) were used. The level of statistical significance was set at P < .05.

Results

Reference ranges of hematologic constituents of the blood of the Brazilian donkey breed determined in the current study are shown in Table 1 and Table 2. Most of the values had Gaussian distribution (P < .10). Only basophils did not seem to be normally distributed (P < .05). Comparisons of hematologic ranges of the Brazilian donkeys with other donkey breeds and populations are shown in Table 1 and Table 2.     

Association of Season and Pasture Grazing with Blood Hormone and Metabolite Concentrations in Horses with Presumed Pituitary Pars Intermedia Dysfunction

Background: Pituitary pars intermedia dysfunction (PPID) is a risk factor for pasture‐associated laminitis, which follows a seasonal pattern. Hypothesis: Hormonal responses to season differ between PPID and unaffected horses. Animals: Seventeen horses aged 8–30 years (14 horses ≥ 20 years of age). Methods: Longitudinal observational study. Blood was collected monthly from August 2007 until July 2008 after pasture grazing and again after overnight stall confinement. Blood hormone and metabolite concentrations were measured and pasture grass samples were analyzed to determine carbohydrate content. Analysis of variance analysis for repeated measures was performed. Results: Mean ACTH concentrations varied significantly over time (P < .001), with higher concentrations detected in August, September, and October compared with November–April. Pasture × time effects were detected for glucose and insulin concentrations, with peaks observed in September. Horses were retrospectively allocated to PPID (n = 8) and control (n = 9) groups on the basis of plasma ACTH concentrations. Changes in insulin concentrations over time differed in the PPID group when compared with the control group. Insulin concentrations were positively correlated with grass carbohydrate composition. Conclusions and Clinical Importance: PPID did not affect the timing or duration of the seasonal increase in ACTH concentrations, but higher values were detected in affected horses. Insulin concentrations differed between groups, but hyperinsulinemia was rarely detected. Glucose and insulin concentrations peaked in September when horses were grazing on pasture, which could be relevant to the seasonal pattern of laminitis.     

Antagonism of Detomidine-Induced Sedation,Analgesia, Clinicophysiological,and Hematobiochemical Effects in Donkeys Using IV Tolazoline or Atipamezole

The present study aimed to investigate and evaluate the reversal of sedation, analgesia, ataxia, clinicophysiological findings, and hematobiochemical effects of detomidine by subsequent IV administration of tolazoline or atipamezole to improve safety and utility of detomidine in donkeys. Six mature donkeys weighing 250–300 kg and aged 4–6 years were used on three separate occasions. Each donkey received the following three treatments at the rate of one treatment per week in a randomized crossover study. The first group received 0.04 mg/kg bwt detomidine. The second group received 0.04 mg/kg bwt detomidine followed by 4.0 mg/kg bwt tolazoline. The third group received 0.04 mg/kg bwt detomidine followed by 0.4 mg/kg bwt atipamezole. Sedation, analgesia, ataxia, pulse rate, respiratory rate, and rectal temperature were recorded at 5 minutes before, then at 5, 15, 30, 60, and 90 minutes after injections. Red blood cell and white blood cell counts, Packed cell volume (%), hemoglobin, total protein, cholesterol, glucose, urea, aspartate amino transferase, alanine amino transferase, and gamma glutamyl transferase values were determined. Detomidine induced deep sedation, complete analgesia, and significant ataxia. Pulse and respiratory rates were decreased from the base line values, although rectal temperature was within the baseline value. The alterations in hematological and hematobiochemical parameters were mild and transient.     

Circannual variation in plasma adrenocorticotropic hormone concentrations in the UK in normal horses and ponies, and those with pituitary pars intermedia dysfunction

Reasons for performing study: Pituitary pars intermedia dysfunction (PPID) is a common endocrinopathy, frequently diagnosed via plasma adrenocorticotropic hormone (ACTH) concentrations. Seasonal variation in plasma ACTH concentrations has been described in normal horses prompting caution in diagnosing PPID at certain times of the year. The aims of this study were to determine appropriate reference intervals for equine plasma ACTH throughout the year; and to examine the circannual variation of plasma ACTH concentrations in PPID cases. Hypothesis: Plasma ACTH can be used as a test for PPID throughout the year with the use of appropriate reference intervals. Methods: Data for reference interval calculations were obtained from samples collected from inpatients of Liphook Equine Hospital (non‐PPID group, n = 156). Data from PPID cases (n = 941) were obtained from samples submitted to the Liphook Equine Hospital Laboratory from horses with a clinical suspicion of PPID found to have plasma ACTH concentrations greater than our upper reference interval for that time of year. Results: Upper limits for reference interval of plasma ACTH were 29 pg/ml between November and July and 47 pg/ml between August and October. Circannual variation in plasma ACTH occurred in both non‐PPID and PPID horses with the highest ACTH concentrations found between August and October in both groups (P<0.0001). The greatest difference between the 2 populations also occurred between August and October. Conclusions: Plasma ACTH can be used for the diagnosis and monitoring of PPID throughout the year with the use of appropriate reference intervals. These findings demonstrate an increase in pituitary gland secretory activity during the late summer and autumn in both normal and PPID cases.     

马驴养殖福利研究进展

动物福利是国内外学者热议的话题,也是标准化生产和畜产品质量安全的重要影响因素。动物福利体现在饲养、养殖环境、健康、行为等各个环节中。马驴作为中国重要的草食家畜,在精准扶贫和乡村振兴中发挥着重要作用。该文阐述了马驴养殖的经济价值,对中国马驴养殖福利现状和动物福利在马驴养殖中的相关影响因素进行探讨,为宣传、提升马驴养殖福利提供一些参考。     

Influence of Transportation on the Serum Concentrations of the Cardiac Biomarkers Troponin I and Creatine Kinase-myocardial Band (CK-MB) and on Cortisol and Lactate in Horses

The objective of this study was to determine the influence of transportation on the serum concentrations of the cardiac biomarkers troponin I (cTnI) and creatine kinase-myocardial band (CK-MB) and on cortisol and lactate in horses. For this purpose, 10 horses were transported for 300 km. Blood samples were collected 24 hours before transport (T0), just before transport (T1), during transport at 50 km (T2), 100 km (T3), 200 km (T4), and 300 km (T5). An additional blood sample (T6) was collected 24 hours after transport. The median resting basal cTnI values in the horses were at T0, 0.000 ± 0.007 ng/mL and at T1, 0.01 ± 0.007 ng/mL. The median resting basal CK-MB values in the horses were at T0, 0.19 ± 0.05 ng/mL and at T1, 0.16 ± 0.05 ng/mL. Statistical analyses showed no significant differences of cTnI and CK-MB among the measured values (T0–T6). On the other side, the cortisol and lactate concentrations increased significantly (P < .01) at T2, T3, T3, and T4 compared with the resting values at T0. At T6, cortisol and lactate concentrations had returned to pretransport values, with no statistically significant differences compared with pretransport concentrations. In conclusion, the 300-km transportation of the horses did not influence the levels of the cardiac biomarkers, cTnI and CK-MB. The serum concentrations of cortisol and lactate, on the other side, increased significantly. The possible influence of transportation for longer distances or under more stressful conditions (higher temperature or in horses not used for transportation) on cTnI and CK-MB concentrations needs to be further investigated.     

Effects of dexamethasone,glucose infusion,adrenocorticotropin, and propylthiouracil on plasma leptin concentrations in horses

In experiment 1, nine light horse geldings (three 3 x 3 Latin squares) received dexamethasone (DEX; 125 microg/kg BW, i.m.), glucose (0.2 g/kg BW, i.v.), or nothing (control) once per day for 4 days. DEX increased (P < 0.001) glucose, insulin, and leptin concentrations and resulted in a delayed increase (P < 0.001) in IGF-I concentrations. In experiment 2, mares were similarly treated with DEX (n = 6) or vehicle (n = 6). DEX again increased (P < 0.01) glucose, insulin, and leptin concentrations; the delayed elevation in IGF-I concentrations occurred on day 10, 12, and 19, relative to the first day of treatment. In experiment 3, six light horse geldings received either 200 IU of adrenocorticotropin (ACTH) i.m. or vehicle twice daily for 4 days. ACTH increased (P < 0.001) cortisol concentrations. Further, ACTH resulted in increases (P < 0.01) glucose, insulin, and leptin concentrations. In experiment 4, plasma samples from four light horse stallions that were fed 6-n-propyl-2-thiouracil (PTU) at 6 mg/kg BW for 60 days to induce hypothyroidism were compared to samples from control stallions. On day 52, stallions receiving PTU had lower concentrations of thyroxine (P < 0.05) and triiodothyronine (P < 0.01) and higher (P < 0.01) concentrations of TSH. Leptin concentrations were higher (P < 0.01) in PTU-fed stallions from day 10 through 52. In conclusion, circulating concentrations of leptin in horses was increased by administering DEX. Treatment with ACTH increased cortisol and resulted in lesser increases in leptin, glucose, and insulin. In addition, PTU feeding results in lesser increases in leptin concentrations.     

Feed efficiency and body composition are related to cortisol response to adrenocorticotropin hormone and insulin-induced hypoglycemia in rams

Metabolic rate and energy consumption increase through the activation of the hypothalamic-pituitary-adrenal axis when an animal is exposed to a stressor. Residual feed intake (RFI) as a measure of efficiency has been shown to be related to exogenous adrenocorticotropin hormone (ACTH)-stimulated cortisol concentrations, which is indicative of the relationship between an animal's response to stress and the efficiency with which the energy is used for growth and production. In this study, we tested the hypothesis that sheep with low post-ACTH serum cortisol concentration relative to the other sheep in the flock have lower RFI values and lower cortisol concentrations following insulin-induced hypoglycemia. Adrenocorticotropin hormone (2.0 μg/kg body weight)-stimulated cortisol concentrations were measured in 100 sheep. The extreme responders were selected (n = 12 high cortisol, n = 12 low cortisol), and feed efficiency and body composition parameters were measured. A second ACTH challenge and an insulin challenge were administered. More efficient sheep (more negative RFI value) were found to have lower (P < 0.05) cortisol concentrations following both an ACTH challenge and an insulin challenge. Low-cortisol sheep (low response to ACTH or insulin) were found to have a lower (P < 0.05) proportion of fat tissue in comparison to the high-cortisol animals. These data clearly indicate that an animal's response to exogenous ACTH or insulin-induced hypoglycemia as a stressor is related (P < 0.05) to efficiency of energy use when measured as RFI. These data have important implications in enabling identification of animals that are superior in terms of feed efficiency and for understanding the physiological mechanisms underlying efficiency of energy use.     

The impact of maternal overnutrition and obesity on hypothalamic-pituitary-adrenal axis response of offspring to stress

We evaluated the effect of maternal obesity before and throughout gestation on offspring hypothalamic-pituitary-adrenal axis function. Multiparous Rambouillet by Columbia crossbred ewes were fed either 100% of National Research Council (NRC) recommendations (control, C) or 150% of NRC recommendations (obese, OB) from 60 d before mating until lambing. Ten lambs born to OB ewes (five males and five females), and eight lambs born to C ewes (three male and five female) were studied. From delivery to weaning lambs were maintained with their mothers, who were all fed 100% NRC recommendations. After weaning, all lambs were group housed and fed the same diet to meet NRC requirements. At 19 mo of age lambs were placed in individual pens and fed a pelletized diet to meet maintenance requirements. Jugular vein catheters were placed and 2 d later lambs received an intravenous (i.v.) adrenocorticotropic hormone (ACTH) challenge followed by an i.v. corticotropin-releasing hormone (CRH)/arginine vasopressin (AVP) challenge 1 d later. Thirty d later offspring were again catheterized and placed into metabolism crates for 2 d before receiving an isolation stress test. ACTH and cortisol responses to the isolation stress test and CRH/AVP challenge and cortisol responses to ACTH challenge were determined. Cortisol was quantified via radioimmunoassay and ACTH was quantified using an Immulite 1000; both were analyzed using repeated measures using the MIXED procedure of SAS. Offspring from OB ewes had elevated basal plasma ACTH and cortisol compared with C offspring before all three challenges (P < 0.05). Offspring from OB mothers tended (P = 0.06) to have a greater ACTH response after an i.v. CRH/AVP injection than offspring from C mothers (12,340 ± 1,430 vs 8,170 ± 1,570 area under the curve, respectively). Cortisol response to the CRH/AVP and ACTH challenges was not influenced by maternal nutrition (P = 0.46) and averaged 4.77 ± 0.2 μg/dL and 1.94 ± 0.01 μg/dL, respectively. The ACTH response following the isolation stress test was also similar (P = 0.82) for OB and C offspring (147 ± 20 pg/mL), and cortisol response during the isolation stress test was similar between C and OB offspring (P = 0.64, 5.25 ± 0.3 μg/dL). These findings suggest that maternal obesity before and during gestation does not affect stress responses by the offspring, but has an impact on hypothalamic-pituitary-adrenal sensitivity. The lack of differences in cortisol release under the influence of difference concentrations of ACTH during the CRH/AVP challenge could indicate adrenal dysfunction in OB offspring.     

Das Gebiß des Hausesels (Equus asinus asinus L.) Morphologisdie und röntgcnologische Untersudiungen

In three donkeys the postnatal development of the teeth was studied at close intervals up to two years of age in one case and up to 5½ years in the other two cases. The findings were checked against the teeth in fÜrther 27 donkeys of known ages and two donkeys of estimated ages. The incisors were studied primarily by inspection and palpation, but also radiographically; whilst the cheekteeth were examined mainly radiographically.
The teeth of the donkey are narrower than those of the horse, and their replacement occurs about 3 months later than in the horse.     

Adrenocorticotropin concentration following administration of thyrotropin-releasing hormone in healthy horses and those with pituitary pars intermedia dysfunction and pituitary gland hyperplasia

OBJECTIVE: To compare the effect of thyrotropin-releasing hormone (TRH) administration on endogenous ACTH concentrations in healthy horses and those with pituitary pars inter-media hyperplasia and compare the test with the dexamethasone suppression test (DST). DESIGN: Prospective case series. ANIMALS: 15 horses with clinical signs of pituitary pars intermedia dysfunction (PPID), 4 horses with equivocal signs of PPID, and 29 horses without signs of PPID. PROCEDURES: ACTH concentrations prior to and after administration of TRH were measured 61 times in 48 horses. Results of the DST (cortisol response) were compared with those of the TRH test in 29 horses. Thirty-three horses (24 with no clinical signs of PPID, 5 with clinical signs of PPID, and 4 with equivocal clinical signs of PPID) were euthanized and necropsied and their pituitary glands evaluated. RESULTS: ACTH concentrations increased in all horses, but magnitude and duration of increase were significantly higher in horses with PPID. Endogenous ACTH concentrations were influenced by season. The ACTH baseline concentrations and response to TRH were not correlated with results of the DST. Results of DST were abnormal only in clinically abnormal horses or those with pars intermedia hyperplasia, but were within reference range in 17 of 26 tests in these horses. CONCLUSIONS AND CLINICAL RELEVANCE: The ACTH response to TRH is a useful test for diagnosis of pituitary gland hyperplasia, particularly in horses in which baseline ACTH concentrations are within reference range. The DST was specific but not sensitive and was inconsistent for individuals, and results often did not agree with the TRH test response.     

Differential responses of Equus caballus and Equus asinus to infection with two pathogenic strains of equine infectious anemia virus

Most in vivo studies with equine infectious anemia virus (EIAV) have been performed in horses and ponies (Equus caballus) with little published information available detailing the clinical responses of donkeys (Equus asinus) to infection with this virus. Consequently, donkeys were inoculated with two strains of EIAV (EIAV(PV) and EIAV(WY)) which have been documented to produce disease in E. caballus. Four ponies, 561, 562, 564 and 567 and two donkeys, 3 and 5 were infected with EIAV(PV) and one horse (94-10) and one donkey (4) were infected with EIAV(WY). Although the horse and ponies all experienced clinical signs of disease, which in some cases were severe, the donkeys remained asymptomatic throughout a 365-day observation period, except for mild transient reductions in platelet counts. The results from serological assays, virus isolation from plasma and detection of plasma-associated viral RNA by RT-PCR, indicated that initial replication of EIAV(PV) and EIAV(WY) was lower in donkeys than in horses and ponies. This conclusion was confirmed using competitive RT-PCR, in which viral RNA levels in the plasma of EIAV(PV)-infected ponies was up to 100,000-fold higher than in infected donkeys during the first 20 days post-infection (dpi). Similar results were obtained in the EIAV(WY)-infected animals, in which viral RNA burdens in the donkey at 20 dpi were 1000-fold less than in the horse. However, infection of donkey and horse monocyte-derived macrophage cultures with EIAV(PV) demonstrated that these cells in vitro were equally susceptible to virus-induced cytopathic effects and yielded similar levels of progeny virus. This result suggests that factors other than host cell permissiveness mediate the clinical differences observed between horses and donkeys infected with EIAV(PV) or EIAV(WY).